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Date:   Fri, 8 Apr 2022 11:59:25 +0200
From:   Michal Hocko <mhocko@suse.com>
To:     Nico Pache <npache@redhat.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Rafael Aquini <aquini@redhat.com>,
        Waiman Long <longman@redhat.com>, Baoquan He <bhe@redhat.com>,
        Christoph von Recklinghausen <crecklin@redhat.com>,
        Don Dutile <ddutile@redhat.com>,
        "Herton R . Krzesinski" <herton@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Ingo Molnar <mingo@redhat.com>,
        Joel Savitz <jsavitz@redhat.com>,
        Darren Hart <dvhart@infradead.org>, stable@kernel.org
Subject: Re: [PATCH v8] oom_kill.c: futex: Don't OOM reap the VMA containing
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On Fri 08-04-22 05:40:09, Nico Pache wrote:
> 
> 
> On 4/8/22 05:36, Michal Hocko wrote:
> > On Fri 08-04-22 04:52:33, Nico Pache wrote:
> > [...]
> >> In a heavily contended CPU with high memory pressure the delay may also
> >> lead to other processes unnecessarily OOMing.
> > 
> > Let me just comment on this part because there is likely a confusion
> > inlved. Delaying the oom_reaper _cannot_ lead to additional OOM killing
> > because the the oom killing is throttled by existence of a preexisting
> > OOM victim. In other words as long as there is an alive victim no
> > further victims are not selected and the oom killer backs off. The
> > oom_repaer will hide the alive oom victim after it is processed.
> > The longer the delay will be the longer an oom victim can block a
> > further progress but it cannot really cause unnecessary OOMing.
> Is it not the case that if we delay an OOM, the amount of available memory stays
> limited and other processes that are allocating memory can become OOM candidates?

No. Have a look at oom_evaluate_task (tsk_is_oom_victim check).

-- 
Michal Hocko
SUSE Labs